FR2690363A1 - Rendering inert material contg. toxic or contaminating components, e.g. heavy metals - by metallurgical fusion, and treatment of industrial or municipal waste by pyrolysis and fusion - Google Patents

Abstract

A (partly powder) material contg. toxic and/or contaminating elements e.g, heavy metals, is rendered inert by metallurigcal fusion in a furnace of the type used in non-ferrous metallurgy, to trap the heavy metals either in the matte, the compsn. of which can be chosen so as to be usable in a metallurgical cycle, e.g, refining, or in the insolubilised metallurgical scoria or slag, with many applications. Also claimed is a process for rendering industrial and/or municipal waste inert involving incineration of the waste to pyrolyse the organic prods. and volatilise volatile components in a controlled atmos., fusion, using the ashes from the incineration, post-cumbustion of the gases formed in the incineration and the fusion, and stepwise condensation of the totally oxidised gases from the post-combustion, to recover the volatile components. ADVANTAGE - The heavy metals can be utilised again. The process limits contamination of the environment.

Description

PROCESS FOR THE INERTAGE OF A POWDERY MATERIAL AND
APPLICATION OF THIS PROCESS TO THE TREATMENT OF UNUSUAL WASTE
TRIELS AND / OR URBAN.

The present invention relates to a method for inerting a pulverulent material capable of containing toxic elements and / or contaminants, such as heavy metals, as well as the application of this method to the treatment of industrial and / or urban waste.

In general, we know that for several decades the treatment of waste and, in particular, industrial and / or urban sludge, has developed considerably and, to this end, many solutions have been proposed and tested.

 It turns out that the experience acquired thanks to these achievements, some of which have been in operation for a good number of years, reveals new, more specific problems, which are incompatible with the evolution of current rules and standards for the protection of the environment. 'environment.

However, the solutions currently proposed for solving these problems are not really satisfactory.

Thus, when incineration of sludges containing a contaminating load of heavy and volatile metals is carried out, these heavy metals are found both in the incineration ash and in the dust suspended in the combustion gases. The new problem which then arises relates to the presence and stability of these metals in this ash and in this dust.

At present, the only solution to this problem is to store ash and dust in special landfills, which, for easily understandable reasons, will quickly cease to be tolerated.

The invention therefore more particularly aims to solve these problems.

To this end, it proposes to carry out on the pulverulent materials of which it is desired to inert the heavy metals, a metallurgical treatment of fusion in an oven of the type of those used in the metallurgy of non-ferrous metals, and this, so as to trap heavy metals, either in mattes or bullions whose composition can be chosen so that they can be used in a metallurgical cycle, for example refining, or in insolubilized metallurgical slag or slag, usable in many applications.

It can therefore be seen that not only does the invention solve the problems mentioned above, but also it provides a revalorization of the heavy metals which we have hitherto sought to get rid of.

This process is perfectly suited to the treatment of industrial and urban waste and sludge.

In this case, the method according to the invention successively comprises the incineration of said sludge and said waste in an industrial furnace then a metallurgical melting treatment of the type of that previously described.

Advantageously, the combustion gases, generated during the incineration phase and the metallurgical melting treatment phase, will undergo an additional oxidation phase in an afterburner chamber before undergoing a treatment comprising a collection, by staged condensation volatile elements.

An embodiment of the invention will be described below, by way of non-limiting example, with reference to the accompanying drawing in which
The single figure is a diagram representation
tick from a sludge treatment plant
industrial and / or urban.

In this installation, the sludge is first of all treated in a vertical oven with stages 1 making it possible to ensure the pyrolysis of the organic products and the volatilization, as complete as possible, in a controlled atmosphere, of the volatile elements (As, Sb, S ...).

The ashes resulting from this combustion are then transmitted to a treatment oven 2 of the type used in the metallurgy of non-ferrous metals such as copper or lead.

Preferably, one uses a melting furnace "low furnaces" with double walls cooled by water "Water-Jacket" operating according to the principle of the granulated beds and in which the ashes are mixed with coke to which a flux is added, the balance thermodynamics being ensured thanks to the addition of copper products.

 It turns out that this furnace is particularly suitable, in its operating principle, for supporting significant arsenical charges which can come either from the mineralogical association with copper, or from specific arsenic waste. Such impurities can then be selectively upgraded by treating the gases resulting from the combustion.

In practice, the capacity of this furnace is only occupied by around 50% by the payload, the balance of the supply being able to be reserved for waste of other kinds, provided that this waste has a metal load. , compatible with the products that we want to promote in the "low furnace".

In fact, the main recoverable elements are: copper, lead, zinc, iron, nickel, cerium, tin, aluminum, bromine, arsenic, antimony and silicon. To these elements, it is advisable to add the alkalis and the alkaline-earths.

According to the thermodynamic balances matte / slag, some of these metallic elements are found in the matte, either as an element improving on the commercial level (like, for example, copper), or as a penalizing element (nickel, arsenic, antimony). Other elements are scorified (iron, zinc, aluminum, silicon, calcium, ...) and thus insolubilized.

Of course, the invention is not limited to the use of a "low furnace" melting furnace of the type of that previously described.

Indeed, it is also possible to use an electric melting furnace 3 (indicated in broken lines in the figure) comprising carbon electrodes immersed in the molten metal bath.

Such an oven is more particularly suitable in the case of ashes whose heavy metal contents are incompatible with the type of treatment carried out in the "low furnace
In such an oven, the principle of which is based on the difference between the energies of formation of metal oxides (Ellinghann diagram), the electric power is dissipated by the Joule effect in the molten slag.

A certain percentage of reducing elements (such as, for example, carbon) are added to the charge so that the most reduced elements are found in the metal bath and the most oxidizable elements are found in the slag.

Therefore, all the metallic elements are trapped, either in a metallic phase (metallic bullion), the composition of which can be chosen so that it is salable or recyclable, or in a metallurgical slag or slag based on iron silico-aluminate and lime where they are insolubilized and suitable for use in shot blasting or simple deposition.

The gases released in the furnace 1 as well as in the "low furnace" 2, or even the electric furnace 3, are collected and transmitted to an afterburner chamber 4 where they are completely oxidized during an exothermic reaction.

The gases thus oxidized are then brought into a treatment unit 5 provided with coolers, in which the volatile elements are collected by staged condensation.

Depending on their composition, these volatile elements are either marketable, recycled, or reinjected into the melting furnace 2, so as to ensure inter-element separation by difference in oxidability.

In the last cooling stages, when there are high arsenic contents, this is condensed in the form of powdered arsenious anhydride As203. It is then packaged in barrels and sold.

In the event that loads of mercury are present in the ashes, the feed must be sorted and the melting treatments carried out selectively so as to dissociate the presence of arsenic and antimony from that of mercury, because it is currently impossible to avoid co-condensations.

Furthermore, in the case of mercury charges, the treatment of gases is carried out in a specific unit specially adapted to this toxic element.

The purification of arsenic oxide As203 may be made necessary by the presence of chlorine from the combustion of certain plastics as well as by the presence of basic sulfates.

This purification is done in an aqueous way so as to dissolve the various salts. The arsenical waters as well as that coming from the possible neutralization of the fumes are treated in a water purification station 6 generating its own sludge which can be entirely recycled in the installation previously described.

Claims (8)

Claims  1. A method for inerting an at least partly pulverulent material capable of containing toxic and / or contaminating elements, such as heavy metals, characterized in that it consists in carrying out on said materials a metallurgical fusion treatment in an oven of the type used in the metallurgy of non-ferrous metals, in such a way as to trap heavy metals, either in mattes or bullions, the composition of which can be chosen so that they are usable in a metallurgical cycle, for example refining, either in insoluble metallurgical slag or slag, usable in numerous applications.  2. Method according to claim 1, characterized in that the above melting treatment is carried out in an oven of the "low furnace" type with double walls cooled by water "Water-Jacket".  3. Method according to claim 2, characterized in that the oven operates on the principle of granulated beds, the thermodynamic balance being ensured by the addition of copper products.  4. Method according to claim 1, characterized in that the above-mentioned melting treatment is carried out in an electric oven comprising carbon electrodes immersed in the molten metal bath.  5. Method according to claim 4, characterized in that, during the melting treatment, is added to the charge introduced into the furnace a certain percentage of reducing elements such as, for example, coal, so that the most reduced are found in the metal bath and the most oxidizable elements, in the slag.  6. Method according to one of the preceding claims, characterized in that the gases released during the fusion treatment are completely oxidized in an afterburner chamber and are then treated in a treatment unit provided with coolers in which the volatile elements are collected by stage condensation.  7. Method according to one of the preceding claims, characterized in that the material to be treated comprises ash from the incineration of various materials.  8. A method for inerting industrial and / or urban waste, characterized in that it comprises an incineration treatment of said waste so as to ensure the pyrolysis of organic products and the volatilization in a controlled atmosphere of volatile elements, a treatment according to one of the preceding claims, ash from the incineration phase, a post-combustion treatment of the gases generated during the incineration and fusion treatments, and a stepwise condensation treatment of the gases fully oxidized as a result post-combustion, for the recovery of volatile elements.